One common type of communications module is a radio module used as a wireless LAN adapter (also referred to as a client adapter). Radio modules provide transparent wireless data communications between fixed, portable, or mobile devices and other wireless devices or a wired network infrastructure.
The primary function of the radio modules is to transfer data packets transparently through a wireless infrastructure. The radio modules operate similar to standard wired network communication devices, except that a cable is replaced with a radio connection. In general, no special wireless networking functions are required, and all existing applications that operate over a network operate using the radio modules.
Radio modules typically take such forms, including, but not limited to adapters commonly referred to as: (i) an extended type II PCMCIA client adapter (also known as a “PC card” client adapter), (ii) a regular type II PCMCIA client adapter (also known as an “LM card” client adapter), and (iii) a PCI client adapter. An extended type II PCMCIA client adapter is a PCMCIA card radio module that can be inserted into any device equipped with an external Type II or Type III PC card slot. Host devices may include laptops, notebook computers, personal digital assistants, and hand-held or portable devices. A regular type II PCMICIA client adapter is a PCMCIA card radio module that can be inserted into any device equipped with an internal Type II or Type III PC card slot. Host devices usually include hand-held or portable devices. A PCI client adapter is a client adapter card radio module that can be inserted into any device equipped with an empty PCI expansion slot, such as a desktop computer.
It should be understood that the term communications module, as used herein, refers to radio modules (including the three different types of client adapters discussed above), as well as other types of communications modules, including but not limited to global positioning devices of a global positioning system (GPS), modems, ethernet adapters, and USB PCMCIA adapters. It should be further noted that the term “workstation” (or “station”), as used herein, refers to a computing device with an installed communications module.
A typical radio module includes a radio and a radio antenna. For example, the radio may take the form of a direct-sequence spread spectrum (DSSS) radio that operates in the 2.4-GHz license-free Industrial Scientific Medical (ISM) band, in accordance with IEEE 802.11b. The radio antenna, for example, may take the form of a permanently attached diversity antenna. In the case of an extended type II PCMCIA client adapter, a built-in antenna is typically housed within the section of the radio module that extends outward from a PC card slot when the radio module is installed. In the case of a regular type II PCMCIA client adapter, the antenna is connected via an external connector. If a snap-on antenna is used, it is typically operated in diversity mode. PCI client adapters commonly include a 2-dBi dipole antenna that attaches to the adapter's antenna connector. However, other types of antennas may be used.
At present, many wireless communication systems, such as wireless local area networks (LANs), are being standardized around two radiofrequency (RF) bands, namely the 2.4 GHz ISM (Industrial, Scientific and Medical) bands, in accordance with IEEE 802.11b, and the 5 GHz UNII (Unlicensed National Information Infrastructure) band, in accordance with 802.11a. The IEEE 802.11b standard uses traditional spread-spectrum technology, whereas the IEEE 802.11a standard uses a frequency division multiplexing scheme known as OFDM (orthogonal frequency division multiplexing).
As both types of wireless communication systems are deployed, there is a growing need for a communications module (i.e., dual band radio module) which is suitably adaptable for communication using either of the frequency bands. Such a communications module will be inherently more expensive and consume more power than a communications module adapted for only one frequency band. Moreover, such a communications module presents problems in laying out a printed circuit board (PCB) to accommodate communications using both frequency bands.
The present invention addresses these and other drawbacks of prior art communications modules.